Flat roof gurus....

I’d like to get some good comments on what you guys look for when inspecting a flat roof. More specifically, the area of past patch attempts, what is considered proper. I know there are lots of different materials out there, and the obvious things that should or should not be present, such as pooling, flashing around the parapets, etc. It’s the little detail things that I’d like more info on. What are you guys seeing that may get overlooked?